This is a competitive renewal application for a multi-disciplinary Center for Sexually Transmitted Diseases at the University of north Carolina at Chapel Hill (UNC-CH). Investigators from the School of Public health and the School of Medicine campuses of UNC-CH combine their talents in an interactive set of projects that will help to design better strategies to prevent sexually transmitted infections. There are six projects and two support core units. Sparling's Project examines the structure and function of Neisseria gonorrhoea Opa outer membrane proteins. Cannon's Project examines the molecular biology and pathogenic properties of Neisseria gonorrhoea Opa outer membrane proteins. Cohen's Project establishes a human volunteer facility in the General Clinical Research Center of UNC- Hospitals in which defined mutants laking putative virulence factors of Neisseria gonorrhoea are inoculated under controlled conditions into the urethra of male volunteers. The question is whether loss of particular surface proteins critically alters ability to cause infection. Stamm's Project examines the structure and roles in pathogenesis and immunity of certain T. pallidum proteins. Wyrick's Project examines the problem of antigen presentation by epithelial cells infected by Chlamydia trachomatis. Each of these five basic science projects has components of microbiology, molecular biology, and genetics, and most have important components of immunology. Each is relevant to vaccine development against the respective organisms. Thomas's Project concerns the behavior and epidemiology of core high frequency STD transmitters in Wilson County, North Carolina, a rural environment in which STD's are a major and poorly understood problem. With his collaborators he will examine the efficacy of lay health advisors in helping to change behaviors that lead to STD's. These projects will be supported by two cores; an Advisors in helping to change behaviors that Clinical/Microbiology Core which will relate the arenas of behavioral and epidemiologic studies to the basic science projects.